Narrow linewidth tunable DFB laser array for PDM-16QAM transmission

To increase capacity of Long-Haul optical network, digital coherent transmission method is recently launched. Due to progress of multi-valued phase modulation, tunable light sources of narrow spectral linewidth are strongly demanded for local oscillator in optical receiver. While, modulators structure become complicated in optical transmitter, so high power signal sources are required to compensate the insertion loss. We report realization of narrow linewidth (<218 kHz) and high power characteristics (>15.5 dBm) in DFB array integrated tunable light source. Results of PDM-16QAM transmission have been successfully demonstrated.